This study is designed to facilitate identification of high risk, immunosuppressed oncology patients in the Clinical Center when infection due to varicella zoster virus (VZV) is present, and in this context will perform a service for those patients entered into the study. In addition, a mechanism for studying the epidemiology, pathogenesis, and routes of transmission of VZV infection in this patient population is established in this study in the event any of the following occur: 1) A patient with active VZV infection is hospitalized in the Clinical Center; 2) VZV is apparently transmitted from patient to patient, patient to staff or staff to patient; 3) Zoster recurs in an individual patient; and 4) Another outbreak of VZV infection. This protocol outlines the techniques to be used in the assessment and analysis of such events, including: serology, viral cultures, histology, and restriction endonuclease analysis of VZV DNA.